Semiconductor substrate density has continuously increased, and continues to increase. Further miniaturization and increased density in semiconductor substrates has typically relied on a backside metal layer attached to the substrate to provide a common ground for the increasing number of active components on the semiconductor substrate. However, to ensure high fabrication yields the backside metal layer must remain securely attached to the substrate throughout the entire fabrication process and then for years during operation.
One conventional method of adhering a backside metal layer to a substrate relies on forming a backside metal stack having several layers, the first of which must form an adhesive bond with the substrate. For example, an interface layer may be deposited on a bottom side of the substrate followed by a thicker current carrying layer, and finally an outer packaging contact layer. However, fabrication procedures such as semiconductor die singulation and pick-and-place processes subject the semiconductor substrate to very high stresses, especially near the edges and/or corners of the die. Because adhesion of the backside metal stack to the substrate is almost entirely dependent on the adhesive qualities between the substrate and the interface layer, unacceptably low yields are often achieved during fabrication due to the backside metal layer peeling from the semiconductor substrate.